Q: A clinical trial using capsules requires 200 grams of theophylline monohydrate. How many grams of anhydrous theophylline must be used if its label also indicates the presence of .4% water? [mol. wt. anhydrous theophylline = 180; monohydrate theophylline = 198]
Explanation: [Qtl [Cl] =[Q2] [C2 ] [181.8 g] [100%] =[x g] [99.6%] x =181.8 grams of anhydrous theophylline Since the anhydrous theophylline has 0.4% unbound water, it is only 99.6% pure. 200 g 198 (hydrous) x =182.5 g While the differences between 184.5 and 181.1 or 181.8 do not appear significant, the principle of correcting for either waters of hy- dration or unbound water is important. Drugs such as magnesium sulfate, theo- phylline, citric acid, and iron salts often have waters of hydration. The pharmac
Q: The prescription balance needed for weighing chemicals is currently designated as a Class balance by the NBS.
Explanation: The prescription torsion balance designated by NBS as Class III must have a sensitivity requirement (SR) of not greater than 10 mg. This SR allowance is greater than the 6- mg requirement for the former Class A balance. Most Class III balances have a maximum capacity of 60 g rather than the usual 120 g for the Class A. The pharmacist should check the serial plate on the back of the balance to ascertain the limits of the balance. Obviously a balance with an SR of 6 mg is more accurate than one wi
Q: Alcohol is suitable as a solvent for menthol or salicylic acid when preparing which of the following dosage forms? I. lotions II. ointments III. Suppositories
Explanation: Because of the volatility of alcohol, it is not suitable in dosage forms from which it may slowly evaporate. If ingredients were dissolved in alcohol and incorporated into ei- ther ointments or suppositories, crystals of the ingredients would slowly appear on the surface of the dosage unit. However, one would expect alcohol to remain within the lotion formula until placed on the skin.
Q: A physician requests a 0.1% strength of a steroidal cream that is commercially available as a 0.25% strength in a "vanishing cream" base. Which one of the following ointment bases is the best choice as a diluent for this order?
Explanation: Hydrophilic ointment is an O/W emulsion base containing sodium lauryl sulfate, petrolatum, and stearyl alcohol. Of the listed bases, it is closest to a vanishing cream base because such a system is characterized by the presence of an O/Wstearate emulsion.